Why does my powerbook screen go negative, then rain pixels

So this has been happening for a bit now. My room mate turns on his computer and the screen is fine. After about 15 miuntes the screen image basically goes negative for a minute or so. After that little pixels begin to rain down until the entire screen is pixelated.

When it is pixelated I can use an external monitor to view my desktop perfectly, which eliminates the graphics card as the issue in my opinion.

Has anyone ran into this issue before, or know someone who has?

I feel as though he may have himself a very portable desktop now.